Major Topic Two: Nutrition
Chapter Eight
Glucose and Diffusion--diabetes (Powerpoint Presentation)
Digestion(pages 144-150)
Nutrition and Diet (page 166)
Food (Powerpoint Presentation)
Glucose and Diffusion
Glucose and diffusion deliver nutrients to cells. Glucose is the main chemical burned or combined with oxygen in cellular respiration.
We all need energy to function. We get this energy from the foods we eat. The most efficient way for cells to harvest energy stored in food is through cellular respiration, a pathway for the production of adenosine triphosphate (ATP). ATP, a high energy molecule, is expended by working cells. Cellular respiration has three main stages: glycolysis, the citric acid cycle, and electron transport.
Glycolysis literally means "splitting sugars." Glucose, a six carbon sugar, is split into two molecules of a three carbon sugar. In the process, two molecules of ATP and two "high energy" electron carrying molecules are produced. Glycolysis can occur with or without oxygen. In the presence of oxygen, glycolysis is the first stage of cellular respiration. Without oxygen, glycolysis allows cells to make small amounts of ATP. This process is called fermentation.
The Citric Acid Cycle The Citric Acid Cycle or Krebs Cycle begins after the two molecules of the three carbon sugar produced in glycolysis are converted to a slightly different compound (acetyl CoA). Through a series of intermediate steps, several compounds capable of storing "high energy" electrons are produced along with two ATP molecules. These compounds, known as nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD), are reduced in the process. These reduced forms carry the "high energy" electrons to the next stage. The Citric Acid Cycle occurs only when oxygen is present but it doesn't use oxygen directly. (http://biology.about.com/library/weekly/aa090601a.htm).
Glucose diffuses through a special protein pore on the cell membrane. Insulin is a protein that is secreted by the pancreas into the bloodstream (normally post-meal). Insulin stimulates cells to use glucose in cellular metabolism or to store it in the liver and muscle.
Type I diabetes occurs when no insulin is produced by the pancreas.
Type II diabetes is directly associated with obesity. The cells become resistant to insulin and can't use glucose.
This image shows the regulation of glucose. The image can be found at the following site, which also includes extensive information relating to Type I and Type II diabetes: http://www.scienceinschool.org/2006/issue1/diabetes/
http://www.cdc.gov/diabetes/ This is a great site put together by the Center for Disease Control. It has patient resources, and also resources for healthcare professionals.
Digestion
The organs of the digestive system are located in the GI tract. Digestion requires ingestion, digestion, movement, absorption, and elimination. All parts of the GI tract have four layers: mucosa, submucosa, muscularis and serosa.
This image shows the process of digestion.
Digestion begins in the mouth. The teeth, saliva, and tongue are each part of the process. The espophogus moves food to the stomach.
The stomach expands to store food. It also mixes food with acidic gastric juices. (The juice is made up of pepsin--an enzyme that digests protein).
The small intestine receives bile from the liver and pancreatic juice from the pancreas. Intestinal enzymes complete the cycle of chemical digestion.
Accesory Organs The accessory organs send secretions to the duodenum (first 25 cm of small intestine).
A. The Pancreas produces pancreatic juice with digestive enzymes for carbohydrates, protein, and fat
B. The Liver produces bile, destroys old blood cells, detoxifies blood, stores iron, makes plasma proteins, stores glucose (as glycogen), breaks down glycogen to glucose, produces urea and helps regulate blood cholesterol levels.
C. The Gallbladder stores bile which is produced by the liver.
The Large Intestine is made up of the cecum, the colon, and rectum. The large intestine absorbs water, salts, and some vitamins; forms the feces; and carries out defecation.
Disorders of the large intestine: diverticulosis, irritable bowel syndrome, inflammatory bowel disease, polyps, and cancer.
Nutrition and Diet
Nutrients released by the digestive process should provide us with plenty of energy, essential amino acids and fatty acids, and all necessary vitamins and minerals. Obesity is increasing rapidly, likely as a result of people's poor eating habits. Obesity is associated with diabetes type two and cardiovascular disease.
The food guide pyramid to the left shows foods to minimize and foods to emphasize for balanced health.
-Proteins supply essential amino acids
-Carbohydrates are necessary, but simple sugars and refined starches cause a rapid release of insulin that can lead to diabetes type two
-Unsaturated fatty acids (omega three in particular) are protective against cardiovascular disease
-Saturated fatty acids lead to plaque (blocking of blood vessels)
Food
The United States has lost much of the cultural and spiritual base to its diet. This has resulted in a dramatic increase in obesity and a decline in overall long term health. The manufacturing process of foods also threatens the farming and agricultural ecosystems.
A large amount of packaged food is sold in the United States each day. To the left is an aerial shot of a typical supermarket. (www.wikipedia.com).
According to this site; http://www.acc.org/advocacy/advoc_issues/summary_obesity.htm, nearly 1,200 deaths each day are attributed to poor lifestyle habits such as nutrition.
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